The different characteristics of voice and data traffic are well known in the telecommunications industry. Data traffic is likely to be high bandwidth but bursty. Legacy time-division multiplex (TDM) circuit-based networks, on the other hand, were originally designed to carry voice traffic, which tends to occupy smaller and predictable bandwidths over a longer period of time. With the growth of data traffic outpacing voice traffic, telecommunications network equipment makers and service providers must find ways to still accommodate TDM traffic but provide more bandwidth-efficient mechanisms to transport the TDM traffic and packet and cell data traffic.
Today's multi-service telecommunication network architecture attempts to service and transport TDM, asynchronous transfer mode (ATM), and frame-based packet-switching telecommunication data. To multiplex packet/cell data and TDM data in the access network, a STS-1 level switch that provides the entire bandwidth assignment of the TDM and packet/cell data is typically used to combine the data into a provisioned SONET interface, such as OC48. The switch allows the TDM data to be assigned to any of the timeslots across the entire bandwidth of STS-1 channels. A framer device then creates from the remaining available time-slots concatenated channels in STS-1 increments of arbitrary sizes (e.g., STS-3C, STS-27C, STS-45C, etc.) for the packet/cell data. The result is a single logical transport pipe into which the TDM and packet/cell data are transported.
The evolving telecommunications network is best served by access and transport devices that provide large (1 to 10 Gb/s) packet or cell service ports transmitting and receiving IP (Internet protocol) packets, for example, and legacy TDM (time division multiplexed) service ports (1.5 Mb/s or 45 Mb/s). The packet data and TDM data are combined into a single optical uplink for transport. In existing multi-service access and transport systems that provide combined packet and cell data and TDM data, the cumulative data is combined into a single OC3 to OC48 optical uplink pipe.
It may be seen that the aforementioned conventional implementation has tremendous power dissipation and device size feasibility problems for large bandwidths. Next generation multi-service systems that have large packet/cell aggregate bandwidths (e.g., 16 Gb/s) and large aggregate TDM bandwidths (e.g., 2.5 Gb/s) would require a large STS-1 switch fabric (e.g., 384×384 STS-1 switch) and very complex framer devices. At these exemplary bandwidths, the required uplink capacity is that of an OC192 transport pipe. The resulting system design, constrained by existing ASIC (application-specific integrated circuit) technologies, will result in very large multi-device and multi-circuit card solutions.